Doctor blade structure



March 5, 1935. SCHWARTZ 1,993,352

DOCTOR BLADE STRUCTURE Filed July 19, 1933 2 Sheets-Sheet lv w 1' d /2 March 5, 1935. HWA TZ 1,993,352

DOCTOR BLADE STRUCTURE Filed July 19, 1933 2 Sheets-Sheet 2 3111; Jon fiedJc/Ewarlz 35 Y pw dtn Patented Mar. 5, 1935 PATENT OFFICE I noo'ron BLADE STRUCTURE Fred schwartz, Green Bay, Wis., assignor to Fort Howard Paper Company, Green Bay, Wis., a corporation of Wisconsin Application July 19, 1933, Serial No. 681,211

10 Claims.

The invention relates to doctor blades and vide a doctor blade and holder therefor so related that the doctor blade may when worn be replaced by anew blade, or a repaired blade, without interrupting the operation of the machine with which the blade is used.

I t is a further object of the invention to provide a doctor blade structure providing a novel form of holder. I)

It is a further object of t e invention to provide a doctor blade and holder in which the blade may have a definite projection from the holder and wherein the projection may be predetermined before the blade is placed in the holder.

It is a further object of the invention to provide a removable doctor blade of such character that a new blade may be placed in the holder by a single operator without interrupting the action of the machine. I a

It is a further object of the invention to provide a jig for adjusting the parts of the blade for introduction into the holder so as to prede termine the projection of the blade from the holder within very close limits.

It is a further object of the invention to provide a holder that will hold a thin flexible blade in such a manner as to restrain the springing thereof in use.

Further objects of the invention will apear from the following description when read in connection with the accompanying drawings showing illustrative embodiments of the invention, and wherein:---

Fig. 1 is an end view of the device showing a a fragment of the roll with which it is used;

Fig. 2 is a plan view of the structure of Fig.

1 broken away to shorten the figure;

Fig. 3 is a transverse section of a modified form of the device;

Fig. 4 is a plan view of the blade;

Fig. 5 is an edge view of the structure of Fig. 4;

Figs. 6 and 7 are end and side views respectively of a jig for adjusting the blade parts to predetermine the projection of the blade from the holder; and

Fig. 8 is a detail longitudinal section on line 88 of Fig. 1 showing a new blade being started into the holder abutting the blade already therein whereby to force the latter out of the holder.

As shown the device comprises a supporting member 10 which may be tubular in character for lightness provided with shaft portions 11, 12 projecting at its ends for pivotal support of the holder upon supports not shown.

A fragment of a roll, as a drying, creping, or calendering roll of a paper machine is indicated at 13. with which roll the doctor blade 14 is designed to coact. The blade used in the invention is preferably a thin flexible blade and the holder therefor is shown as comprising spaced opposite portions 15, 16, 17', and 18 designed to engage opposite surfaces of the blade 14 and so spaced apart as to hold the blade in a manner to allow of free longitudinal sliding movement of the blade.

Pressure of the edge of the blade 14 would tend to cause downward bowing of the blade between its roll engaging edge and the portions 17, 18 under pressure at the point 15. To keepthe blade straight between the portions 17,18 and the portion 15, the engaging portion 16 is placed sirearwardly of the portion 15 rather than in reg-- istering opposition thereto. A space 19' is formedin the holder to receive the rear edge of the blade without contact of the edge thereof with the holder.

To move the blade in the holder there is shown a shaft 20 journalled in the holder at 21, 22 having rigidly mounted thereon a pinion 23 at one end and a crank 24 at the opposite end.. To coact with the pinion 23 the blade is provided with a rack bar 25 traveling in a groove 26 in the holder. To adjustably secure the rack bar to the blade there are shown a plurality of screws 27 passing through a bar 28 upon the lower side of the blade through slots 29 in the blade and screwthreaded into the rack bar 25 as clearly shown in Fig. 8. The bar 28 slides in a groove 45 in the lower portion of the holder. 40

pinion 34 and crank 35. The location of the pinions 23 and 34 is preferably such as shown in Fig. 2 that the rack bar carried by the blade 14 in operative position is out of mesh with the pinion 23 but is in mesh with pinion 34. With 37 and the screws 27 are inserted and tightened" '45 this arrangement of parts a single operator may insert a new blade with its ancillary parts into the end of the holder and by turning the crank 24 may feed the new blade into the holder until it abuts the operating blade, as shown in Fig. 8, whereupon continued operation of the crank will feed in the new blade and force out the old blade, the pinion 34 and crank 35 revolving freely.

When the new blade has been fed until its rack bar begins to mesh with the pinion 34, it will be ready to leave the pinion 23 and the operator can then go to the other end of the holder and by manipulation of the crank 34 simultaneously adjust the position of the blade relative to the roll. This operation can be carried out with the machine of which the roll 13 forms a part in continuous operation without interrupting the passage of the sheet of paper thereover.

To lessen the friction of movement of the blade 14 in the holder, the form of surfaces 15'--18 illustrated in Fig. 3 may be adopted.

When a blade has been once used and must be replaced, it is still capable of further use if its edge be trued' up but after such truing the width of the blade will be lessened. To ensure that the blade shall project from the holder, a correctly predetermined distance, the jig of Figs. 6 and 7 is provided by the invention. In said figures there is shown a bar 36having a member 37secured thereto as by cap screw 38 which member 3'7 desirably bears a rib 39 seating in a groove in the bar 36 to accurately determine the position of the edge 40 of the bar 37. A shoulder is provided at 41 at the end of a surface 42 upon which the blade to be set may be laid.

When the jig is to be used, the rack bar is laid in a groove 43 in the jig, the blade 14 is placed upon the surface 42 with its edge in con: tact with the shoulder 41 whereupon thebar 28 is placed against the edge 40 of the member down, the slots 29 in the blade permitting of the locating of the bars 25-28 at the desired place transversely of the blade 14. The assembled blade may then .be fed into the holder with assurance that its edge will be correctly positioned with the surface of the roll.

Lengths of doctor blades for the use intended run up to one hundred inches. A bar, as 28, of this length may be slightly bowed. Therefore the edge 40 of the member 37, which may be made accurately straight, provides a means of truing the bar 28 when it is screwed upon the blade and rack bar. The rack bar will be held truly straight by engagement with the groove 43 of the jig.

Heretofore in all doctor blade structures of which I am aware, when a doctor blade must be replaced it has been necessary to shut down with opposite sides of the blade; said blade free for longitudinal sliding movement in said holder; and means to feed a blade longitudinally into the holder to act by abutment against a blade already in the holder to force the latter 4 therefrom.

2. A doctor blade structure comprising, in combination: a blade holder formed to hold a doctor blade for free longitudinal sliding movement; a doctor blade; a rack bar carried by said blade; said blade and bar slidable in said holder; a pinion journaled on said holder to mesh with the teeth of said rack bar; and means to cause revolution of said pinion.

3. A doctor blade structure comprising, in combination: a blade holder formed to hold a blade for free longitudinal sliding movement and having a longitudinal groove; a doctor blade; a rack bar carried by said blade slidable in said groove; a pinion journaled on said holder to mesh with the teeth of said bar; and means to cause revolution of said pinion.

4. A doctor blade structure comprising, in combination: a thin flexible doctor blade; a holder for said blade formed with opposite registering portions to contact opposite sides of the blade adjacent its irmer edge; said holder formed with a second pair of portions to contact the opposite sides ofthe blade at the outer edge of the holder in staggered relation; the pressure applying portion of the last named pair overhanging the remaining portion of the pair.

5. A doctor blade structure comprising in combination: a thin flexible doctor blade; a holder for said blade formed with opposite registering portions to contact opposite sides of the blade adjacent its inner edge; said holder formed with a second pair of portions to contact the opposite sides of the blade at the outer edge of the holder in staggered relation; the

, pressure applying portion of the last named pair overhanging the remaining portion of the pair, 'said portions formed for substantially line contact with the surfaces of the blade.

6. A-doctor blade structure comprising, in combination: a holder formed to support a doctor blade for free longitudinal sliding movement; a blade; a rack bar carried by said blade; a pinion journaled on said holder with its teeth normally in mesh with the teeth of said rack bar; a second pinion journaled on said holder with its teeth normally out of mesh with the teeth of said rack bar; and means to cause revolution of said pinions independently of each other; whereby a replacement blade may be placed with its rack bar teeth in mesh with the last named pinion and caused to force the operating blade longi tudinally from the holder and the first named pinion may be operated to finally locate the blade in the holder.

7. A doctor blade structure comprising, in combination: a holder formed to hold a doctor blade for free longitudinal sliding movement and having opposed grooves; a doctor blade; a rack bar and a rib clamped upon opposite sides of said blade by screws passing through transverse slots in said blade to permit of adjustment of'their position on the blade; said bar and rib slidable in the respective grooves; a pinion journaled on said holder in position to mesh with the teeth of said rack bar; and means to cause revolution of said pinion.

8. A doctor blade structure comprising, in combination: a thin flexible blade having transverse slots; a bar secured upon said blade by screws passing through said slots; said bar operable to locate said blade in a holder.

9. A doctor blade structure comprising, in combination: a thin flexible blade having transverse r slots; a pair of bars clamped to opposite sides of said blade by screws passing through said slots; rack teeth carried by a surface of one of said bars.

10. A doctor blade structure comprising, in

a blade support having a groove to receive said rib; blade contacting ribs carried by said support rearward of said groove; said support formed with an excess blade width receiving recess rearward of said blade contacting ribs.

FRED SCHWARTZ. 

